The present invention relates to a medium supply device and an image forming apparatus.
In a conventional image forming apparatus such as an electro-photography printer is provided with a medium cassette having a medium placing portion. In general, the medium cassette is arranged to be detachable relative to a main body of the conventional image forming apparatus. The medium cassette includes a first style in which a whole portion of the cassette is completely retained inside the conventional image forming apparatus (completely retained style), and a second style in which only a part of the cassette is retained inside the conventional image forming apparatus (partially retained style).
In the medium cassette of the completely retained style, it is possible to prevent dusts from attaching to a recording medium stored therein. In the conventional image forming apparatus, it is necessary to provide an urging member such as a spring for urging a recording medium toward a sheet supply roller, so that the recording medium is pressed against the sheet supply roller as a medium supply member. In the medium cassette of the completely retained style, it is possible to provided the urging member in the medium cassette itself. That is, the medium cassette is provided with a function of regulating or releasing an urging force of the urging member accompanied with an operation of attaching or detaching the medium cassette to or from the conventional image forming apparatus.
In the past, only a large size and high performance printer or copier is provided with the medium cassette having the function of regulating or releasing an urging force against the recording medium stored therein. On the other hand, most of small and less expensive printers are provided with the cassette of the partially retained style, in which only a part of the cassette is retained inside the conventional image forming apparatus (refer to Patent Reference).    Patent Reference: Japan Patent Publication No. 06-64761
Instead of the medium cassette arranged to be detachable, another conventional image forming apparatus is provided with a medium placing portion integrated with a main body thereof, thereby reducing a cost. In such a conventional image forming apparatus, a sheet supply roller is urged toward a medium, so that it is possible to supply the medium on the medium placing portion.
In the conventional image forming apparatus, the urging force is applied to the medium thus placed all the time. Accordingly, it is difficult to set the medium on the medium placing portion to replenish the medium. That is, when the medium is replenished, it is necessary to set the medium on the medium placing portion after the urging force applied to the medium is released to secure a space between a medium supply member and the medium.
In view of the problems described above, an object of the invention is to provide a medium supply device and an image forming apparatus, in which it is possible to solve the problems of the conventional image forming apparatus. In the present invention, it is possible to easily set a recording medium even when a member for regulating or releasing an urging force against the recording medium is provided in a main body of the image forming apparatus.
Further objects of the invention will be apparent from the following description of the invention.